A need exists for lightweight tubes capable of withstanding large bursting forces. One of the possible uses of such tubes is for rail gun barrels.
In a rail gun, it is desirable that the rails and the adjacent insulating members fit together with very close tolerances and be tightly constrained against displacement outward. A typical, known rail gun barrel assembly employs a large number of bolts to clamp stiff structural members about the barrel components to react bursting forces. Stronger, less cumbersome barrel designs are still being sought, and in other fields of endeavor, there is a demand for lightweight, inexpensive tubes which can successfully contain elevated pressures.
Another area in which a market demand exists for economically-constructed prestressed tubes is that of concrete pipes used for carrying water and other fluids under pressure. Concrete tubes and the like articles can be prestressed either during setting of the concrete or after the concrete has set or hardened.
Further, when the concrete articles are constructed in a tubular form, prestress forces may be applied either from within or without the concrete tube. Examples of prestress forces being applied to the inner bore of a concrete cylinder are given in U.S. Pat. Nos. 2,585,446; 2,709,845; and 3,249,665.
As mentioned, prestress forces may also be applied to the outside of the concrete article. For example, U.S. Pat. No. 2,048,253 disposes the concrete article within metal pressure-retaining plates and forces pressurized water between the metal plates and concrete article to apply a prestressing force. Further, concrete articles may be prestressed by applying or imparting prestress forces to reinforcing members (tendons) typically formed of high tensile strength steel disposed within the concrete articles. The reinforcing members, in turn, impart a prestress to the concrete material. Examples of this type of prestressing are given in the following U.S. Patents: U.S. Pat. Nos. 1,965,748; 2,683,915; 3,260,020; 3,202,740; and 3,567,816.